The present invention relates to a staple feeding apparatus for taking out away from a staple cartridge the lowermost sheet-shaped staple among a plurality of sheet-shaped staples received in the staple cartridge in the multi-layered structure wherein the staple cartridge is fitted into a magazine turnably arranged in a motor driven stapler. In addition, the present invention also relates to a staple feeding mechanism for a motor driven stapler which assures that a plurality of sheet-shaped staples, received in a staple cartridge in the multi-layered structure, are successively taken from the staple cartridge to the foremost end of a magazine in order from the lowermost sheet-shaped staple among the foregoing plurality of sheet-shaped staples received in the staple cartridge.
A hitherto known staple feeding apparatus of the foregoing type is constructed such that a feeding unit, including a feeding belt or a feeding roller disposed below the bottom of a staple cartridge, is arranged in such a manner as to allow the lowermost staple, among a plurality of sheet-shaped staples received in a staple cartridge, to come in tight contact with the upper surface of the feeding belt or the Seeding roller of the feeding unit. As the feeding unit is driven by an electric motor, the lowermost staple is taken from the staple cartridge to reach the foremost end of a magazine turnably arranged in a motor driven stapler (see, e.g., a Japanese patent examined. Publication No. 1-25672).
With the conventional staple feeding apparatus constructed in the above-described manner, the intensity of feeding power required to remove each staple usually varies depending on a magnitude of the frictional resistance present between the lowermost sheet-shaped staple and the upper surface of the feeding unit. The larger the frictional resistance, the larger the feeding power required for the foregoing purpose. Thus, the lowermost staple can be reliably fed from the staple cartridge to the magazine in the presence of the high frictional resistance. Since a plurality of sheet-shaped staple cartridges received in the staple cartridge are normally forced from above by the resilient force of a spring means, a large amount of frictional resistance can be present between the adjacent upper and lower staples. Thus, a malfunction can arise where part of an adhesive, that connects adjacent straight staples staple to each other, adheres to the upper or lower sheet-shaped staple or a staple is partially entangled with the upper or lower sheet-shaped staple. In such a case, a higher amount of feeding power must be applied to the lowermost staple in order to reliably feed it to the magazine after this lower staple is separated from a the staple located above it. In practice, the frictional resistance present between the lowermost staple and the upper surface of the feeding unit is sometimes not large enough to reliably feed the lowermost sheet-shaped staple from the staple cartridge.
In addition, with the conventional staple feeding mechanism constructed in the above-described manner, a drawback is that it becomes complicated in structure since the driving power is required for actuating the staple feeding mechanism is typically generated by the electric motor. To obviate the foregoing drawbacks to a staple feeding mechanism for removing a staple from a staple cartridge when the staple comes in contact with a feeding roller in a feeding that has a ratchet mounted on one end of a roller shaft for the feeding roller, and an actuating unit. The actuating unit includes a pulling pawl and a pushing pawl and is mounted on a pair of driving links. The driving links are adapted to drive a magazine in such a manner that when the driving links are turnably displaced in the downward direction, the pulling pawl is engaged with the ratchet, and subsequently, when the driving links are turnably displaced in the upward direction, the pushing pawl is engaged with the ratchet. Thus, the ratchet rotates during the engagement of the pushing pawl with the ratchet and the staple is delivered in the forward direction by a distance corresponding to the rotation of the ratchet.
With the proposed staple feeding mechanism however, there arises a necessity for arranging an additional unit for normally biasing of the actuating unit toward the ratchet so as to allow the pulling pawl to be reliably engaged with the ratchet. In addition, since the ratchet is rotated by a small angle with each working stroke of the driving links the motor driven stapler should be repeatedly actuated until a staple can be struck by a driver when the staple cartridge is replaced with a new one.